Terbutaline is a 2 adrenergic receptor agonist, used as a "reliever" inhaler in the management of asthma symptoms and as a tocolytic (anti-contraction medication) to delay preterm labor for up to 48 hours. This time can then be used to administer steroid injections to the mother which help fetal lung maturity and reduce complications of prematurity.
Terbutaline as a treatment for premature labor is an off-label use not approved by the FDA. It is a pregnancy category C medication and is routinely prescribed to stop contractions. After successful intravenous tocolysis, little evidence exists that oral terbutaline is effective. However, following uterine inversion in the third stage of labor, terbutaline (or either Halothane or magnesium sulfate) can be used to relax the uterus if necessary prior to uterine replacement.